Study Of Coordinated Control On Suspension Density And Liquid Level In The Dense Medium Coal Preparation

The control precision of the suspension density and liquid level in dense medium coal preparation is directly related to the coal preparation effect.At present,the coal washery usually only pays attention to adjust the suspension density.However,as the production process continues,the liquid level continues to decrease,and the stable control of density cannot be achieved when serious conditions occur.Therefore,it is necessary to study the coordinated control of the suspension density and liquid level in dense media coal preparation.In this dissertation,the coordinated control of the density and liquid level is studied.The main work is as follows:1)For the Shigetai and Zhangcun Coal Washery,by analyzing the influence of the opening change of valves,such as the clean water valve,the add medium valve and the split-flow valve,on the suspension density and liquid level in the dense medium coal preparation,the transfer function model of the density and liquid level with the parameter is established.The transfer function model for density and liquid level is finally determined based on the parameters are identified by the combination of experimental data fitting curves.In the established models,Shigetai Coal Washery is a two-input and two-output model affected by adding water and medium,Zhangcun Coal Washery is a three-input and two-output model affected by adding water,medium and split flow.2)Decoupling control is applied to the two-input and two-output model.Based on the decoupling control,the feed-forward is applied to the three-input and two-output model,with the change of opening the split-flow valve,which is treated as a disturbance and feed-forward compensation is adopted.3)In order to improve the dynamic control performance of suspension density and liquid level,a predictive control algorithm based on the state-space model is used in this dissertation.Firstly,the MOESP in subspace identification is used to identify the state-space model;and then,the objective function is formulated with the quadratic performance index in finite time domain,and the updated state is got by Kalman filtering;finally,the simulation results are compared and analyzed to conclude that the predictive control performance,such as regulation time,overshoot,and robustness,is better than that of the decoupling control.The study on the coordinated control of suspension density and liquid level in the dense medium coal preparation,in this dissertation,have realized the effective adjustment of suspension density and liquid level,and have theoretical significance to solved the problem in the actual production process that the suspension density is difficult to remain stable for a long time.